1. Field
The present disclosure relates to a backlight device and a liquid crystal display apparatus, as well as to a lens, involving light emitting diodes used as a light source.
2. Description of the Related Art
Conventionally in a backlight device for a large-sized liquid crystal display apparatus, multiple cold cathodes are arranged just below a liquid crystal panel. The multiple cold cathodes are used together with members such as a diffuser plate and a reflector plate. In addition, in recent years, a light emitting diode has come to be used as a light source for backlight devices. The efficiency of a light emitting diode has recently increased, and therefore is expected to be a light source having decreased power consumption and replacing a fluorescent lamp. What is more, the brightness level of light emitting diodes used as a light source for a liquid crystal display apparatus can be controlled in accordance with video to lower the power consumption of the liquid crystal display apparatus.
In a backlight device using light emitting diodes as a light source for a liquid crystal display apparatus, multiple light emitting diodes are arranged as a substitute for cold cathodes. If multiple light emitting diodes are used, uniform brightness can be obtained on the surface of the backlight device, but the cost increases because a large number of light emitting diodes are needed. There is an approach for decreasing the number of light emitting diodes to be used by increasing the output of each individual light emitting diode. For example, Patent Literature 1 (Japanese Patent Publication No. 3875247) proposes a lens for obtaining a uniform planar light source with even a small number of light emitting diodes.
In addition, as disclosed in Patent Literature 2 (Japanese Laid-Open Patent Publication No. 2006-286608), a light source is known which includes: a plurality of point light sources one-dimensionally arranged; and elongate cylindrical lenses provided above the plurality of light sources.